Hydrocarbon conversion process



Sept. 2l, 1954 D. H. IMHoFF ETAL 2,689,821

HYDROCRBON CONVERSION PROCESS yfzbjvw 477 kwis/ Sqn. 21, 1954 Filed Oct. 17, 1.950

D. H. IMHOFF ETAL HYDROCARBON CONVERSION PROCESS 3 Sheets-Sheet 2 Sept. 21, 1954 D. H. :Ml-:OFF ETAL 2,689,821

HYDROCARBON CONVERSION PROCESS Filed Oct. 17, 1950 3 Sheets-Sheet 3 474; 575m 01PM, af 7am; iwf 5.

@ma Wa; 62 ya; Af. 0. M61

Patented Sept. 2l, 1954 UNITED STATES attesti Artur ottici:

HYDROCARBON CONVERSION PROCESS of vCaliffsn'nia Application October 17, 1950, SerialNo. 190,496

13 Claims. l

This invention relates generally to 4'the conversion of hydrocarbons in a catalytic contacting process for upgrading such hydrocarbons. More specifically, this invention relates to an improved catalytic hydrogenationprocess wherein a mixture of feed stocks is employed, the one being dehydrogenated and the other undergoing hydrogenation.

Catalytic upgrading of petroleum hydrocarbon stocks is well known in the art and'suchprocesses are employed to effect one or several of such reactions `as hydrogenation, dehydrogenation, aromatization, isomerization, desulfurization and the like. One such catalytic :prccess is termed hydroiorming and employs `any of several catalysts, such as molybdena on alumina catalysts, for effecting'aromatizationo the stock in order to improve `the octane rating. In `this process hydrogen is produced `by the dehydrogenation of the naphthenes and such hydrogen is recycled with the incoming feed to effect `the reaction in a hydrogen-rich atmosphere and minimize coke deposition thereby.

In general the commercial installations of the hydroforiningprocess have employed static catalyst beds to reform straight run stocks. Because of the endothermic nature of the naphthene dehydrogenaticn reaction a large temperature `drop is observed across the reactor bed. The net result is that vthefeed `stock must be heated considerably above ythe optimum hydroforming temperature and the product is withdrawn `at a temperature which is considerably below the optimum hydroiorming temperature.

One possible means for eiecting hydrofo'rming `at substantially a constant optimum temperature would beto employ `a fiuid type catalyst. Such processes, however, are relatively inefficient for effecting certain reactions, e. g., hydroforming because of the channeling which necessarily occurs in a luidized reactor bed. v

Another disadvantage of the prior fart lies in the fact that no `provision -is made for the maxi- :mum utilizaticn of the straight run feed which may be employed `along with the cracked stock. Thus excessive quantities of straight run have been required in ythe past.

This `invention relates to a new method for effecting the catalytic conversion of hydrocarbon stocks at substantially isothermal conditions in moving bed by a suitable control of the concentrations of the reactants at the various levels within the moving bed and also vby controlling the ratio of the two feed stocks, the one cracked `and the other non-cracked, in vorder to vprovide a hydrogen balance.

It is yan object ofthisinventi'on tocontrol the ratio of cracked and straight run feed stocks to a catalytic process so that a substantial balance of "the hydrogen requirement is attained.

It is Aan object of this invention to reform catalytically two hydrocarbon stocks in a moving catalyst fbed wherein `the concentrations oi the reactants are controlled 'so that a desired temperature proiile inthe reactor system is produced.

`It is another object of this invention to process simultaneously cracked fand straight run fractions in `avmo'ving bed of catalyst wherein the ratio of the cracked stock to the straight run is controlled "by a suitable l.process variable.

It is anotherobject of this invention to process a relatively 1claclredand va relatively non-cracked fraction inthe presence Aof a `moving bed'of a cobalt molybdate catalyst whereby 'a substantially saturated product of high octane number is obtained without recourse to outside hydrogen facilities or production.

It is another'object of thisiinvention to provide a `catalytic `process wherein catalyst is conveyed from a `iii-st level to a second level by means of agaslift employing a hydrogen-rich stream, whereby the exhaust lift gas is reduced inhydrogen content by the reduction of the :catalyst and such exhausted lift gas is discharged `from `the system to prevent the build-up of inert gas, such las methane, in the system.

it is another object of =thisiinvention to control the reactor .pressure in a moving bed catalyticfreactor by appropriately varying the ratio ofccracked to straight run feed stocks whereby hydrogen is produced `or consumed to maintain a given desired pressure.

Briefly, the `present invention `comprises an improved catalytic reforming `process which is divided into two major operations, the rst including a reaction step or series of reaction steps wherein hydrogen-containing gases are circulated through a reaction zone and the second including a regeneration step wherein oxygencontainingrgases are circulated over `the catalyst to remove carbondeposits in a regeneration zone. In the preferred form of the invention a catalystis tpassed from one of such operations by means of gravity flow to the other of such operations and the catalyst discharged from the latter -is conveyed to the former by means of `a gas lift. Suitable sealing means are provided to prevent passage of oxygen-containing gases into hydrogen-containing gases.

The present invention eliminates the serious disadvantage of conventional hydroforming or other reforming operations by employing a mixed feed stock, the one being a cracked stock which is relatively rich in olefinic components and the other being a straight run stock which is relatively rich in naphthenes. Under the process conditions the olens are at least partially hydrogenated to produce saturated hydrocarbons therefrom exothermically. Simultaneously the naphthenes are dehydrogenated or aromatized endothermically to produce aromatics. In the operation of the invention either the ratio of the feed stocks or the hydrogen concentration is so controlled that any desired or optimum temperature profile may be maintained throughout the length of the catalyst bed by suitably controlling and varying the rate of the dehydrogenation relative to the rate of hydrogenation.

In one method for effecting temperature control the straight run naphthene-rich stock is introduced at one end ofthe moving catalyst bed along with all or a substantial part of the recycle hydrogen stream. The cracked feed stock is divided into two or more portions and is injected at several levels throughout the catalyst bed in such amounts that the desired temperature prole will result, e. g., isothermal operation.

In another modification of the invention the cracked stoel: and straight run feed stocks are mixed and introduced into the moving catalyst bed. Recycle hydrogen is injected at several levels along the path of vapor flow through the catalyst bed in order to control the relative rate of hydrogenaton and dehydrogenation and thus maintain a desired temperature profile.

Another feature of this invention resides in the methods for supplying the two feed stocks to the reaction zone or zones wherein the ow of the one stock, e. g., the cracked stock, is controlled by a suitable process variable, such as the hydrogen content of the recycle gas, the hydrogen concentration of the recycle gas, the pressure of the reaction Zone, or the like and the other stock, e. g., the straight run stock, is controlled to maintain a constant total flow of feed stock to the reaction Zone or zones or alternatively is controlled to maintain a constant liquid product production rate from the reaction zone or zones.

In the application of this invention two feed stocks are passed into the moving catalyst bed. The first feed stock is generally either of the straight run or of the natural gasoline condensate type or any other relatively naphthene-rich stocks. The naphthene-rich feed stock should normally contain greater than about 30% by volurne of naphthenes and normally should contain less than about 5% by volume of olefinic hydrocarbons. The second feed stock is an olefin-rich stock such as is obtained by catalytic or thermal cracking by pyrolysis, coking, polymerization and the like. Such feed stock will in general contain up to about 3% by weight of sulfur and up to about 0.3% by weight of combined organic nitrogen. The olefin-rich feed stock should preferably contain between about l5 and 70% by volume of olenic hydrocarbons.

The boiling range of the two stocks will normally lie in the gasoline boiling range or slightly higher, such as below about 450 F. In certain instances higher boiling range stocks such as up to about 700 F. or more may be employed if desired.

Catalytic agents which accelerate the dehydrogenation, cyclization, and other reactions occurring in the hydrocarbon reforming operation in- `about 7% and 12%.

clude oxides of vanadium, chromium, molybdenum, and tungsten used alone or oxides of copper and chromium, chromium and molybdenum, and the like used together. The quantity of the catalytic agent in the nished catalyst normally is in the range from about 5% to 25% by weight and preferably in the range between The carrier may be any one of the known refractory oxides including silica, titania, alumina, thoria, zirconia, or mixtures thereof. Of particular merit is a carrier of alumina containing about 5% silica.

The preferred method for preparing the catalysts used in the present invention includes the steps of drying the carrier at C., a calcination for about two hours at 600 C., impregnation of the carrier with a sodium-free aqueous solution containing a soluble compound of the active metal or metals, evaporation of the residual water from the drained carrier at 100 C., and a final calcination of 2 to 6 hours duration at 600 C. When a mixture of elements is employed, as in a copper chromate or cobalt molybdate catalyst, two or more successive impregnation steps are employed each followed by a drying and a calcination step.

Applied to catalytic reforming, these catalysts effect isomerization, hydrogenaton, hydrocracking, desulfurization and aromatization reactions at temperatures between about 800 F. and 950 F. When sulfur-bearing stocks are treated, molybdenum oxide forms metal suldes on the catalyst which are converted to sulfur dioxide on regeneration. The other catalysts named reduce the sulfur of the feed to hydrogen sulfide which is produced with the hydrocarbon product. The process of this invention utilizes each of these catalysts with little modification, with the one exception that when molybdenum oxide is the active agent, a hydrogen reduction step is required following the spent catalyst regeneration to bring the catalyst to its highest degree of activity.

While any of the foregoing catalysts may be employed in the process of this invention, it has been found that catalysts of the cobalt molybdate type are extremely effective for carrying out the process and are therefore the preferred catalysts. Cobalt molybdate type catalysts are extremely resistant to sulfur and nitrogen poisoning and at the same time possess the necessary physical ruggedness to permit their use in a moving bed type operation. Furthermore, the hydrogenaton rate in the presence of a cobalt molybdate catalyst is extremely rapid with the result that extremely fine temperature control can be attained by olefin or hydrogen injection according to the methods of this invention, such as is not so readily obtainable with the aforementioned catalysts.

Cobalt molybdate catalysts in general comprise mixtures of cobalt and molybdenum oxides wherein the molecular ratio of CoO to M003 is between about 0.4 and 5.0. This catalyst may be employed in unsupported form or alternatively it may be distended on a suitable carrier such as alumina, silica, Zirconia, thoria, magnesia, magnesium hydroxide, titania or any combination thereof. Of the foregoing carriers it has been found that the preferred carrier material is alumina and especially alumina containing about 3-8% by weight of silica.

In the preparation of the unsupported cobalt molybdate catalyst the catalyst can be co-prevatedby heating `to about 500 C. Alternatively. the cobalt molybdate may be supported on alumina by co-preoipitating amixture of44 cobalt, aluminum and lmolybdenum oxides. A `suitable hydrogel of the three `components `can be prepared `by adding `an ammoniacal ammonium molybdate solution to an aqueous solution of cobaltand aluminum nitrates. The precipitate whichresults is washed, dried andactivated. In stillanother method a washed aluminumhydrogel issuspended in an aqueous solutionof cobalt nitrate and an ammoniacal solution `of ammonium molybdate isadded thereto, By this means a cobalt 'mo'lybdate gel is precipitated on the alumina gel carrier. Catalyst Apreparations"similar in nature to these and which can alsobeemployed in `this invention have been described in U. S. 'Patents 2,369,432 and 2,325,033.

Still other methods of catalyst preparation may be employed such as by impregnating `a dried carriermaterial, e. g. an alumina-silica gel, with an ammonical solution ofcobalt nitrate andammonium molybdate. Preparations of thistype of cobalt molybdate catalyst are described in U. S. Patent 2,486,361. In yet another method for 'preparing impregnated 'molybdate catalyst the carrier material may be first impregnated with an aqueous solution of cobalt `nitrate and thereafter impregnated with an ammoniacal molyb- "date. Alternatively the carrier may also be iinpregnated with both solutions in reverse order. VFollowing the impregnation of the carrier by any of the'foregoing methods the material is drained. dried and finally activated in substantially 'the same manner as is employed for the other catalysts- In the preparation of impregnated catalysts where separate solutions of cobalt and molybdenum are employed, it has been found that it is preferable to impregnate the Acarrier rst with molybdenum, e. g., ammoniacal ammonium molybdate, and thereafter to impregnate with cobalt, e.lg., aqueous cobalt nitrate, rather than `in reverse order.

-with a suitable pilling lubricant or binder which mixture can then be pilled or otherwise formed `into pills or largeriparticles and activated.

In yet another `modification finely divided or ground molybdic oxide can be mixed with suitably `ground carrier such as alumina, alumina-silica and thelike in the presence of a suitable lubricant orfbinder and thereafter pilled or otherwise V,formed into larger agglomerated particles. These pills or particles are then subjected to a preliminary activation by heating to 600 C., for examplaand are thereafter impregnated with an aqueoussolutionvof cobalt nitrate to deposit the cobalt thereon. After draining and drying the iparticlesfare'heated to about 600 C. to form the catalyst.

It isapparent from the foregoing description of the differenttypes of cobalt `molybdate cata- :lyst which Ymay `be employed in this invention that weimay employ either an unsupported catalyst, in which case the active agents approximate 100% of the composition or we may employ a supported catalyst wherein the active agents,

`cobalt and molybdenum oxides, will generally comprise-from about 7 to 22% `by weight of the catalyst composition In all of the foregoing 6. catalytic lpre'parations lit is desirable tolmaint'ain the molecular Aratio of Icobalt ,oxide was 1Go@ to molybdic oxideias-MoOaibetweeniabout 0.4ean`d5-0.

The reforming reactions `of this invention Amay be carried out at temperatures `betweenabout '8'00 and-950 F. and preferably in theirangeiof 850? to 900 F. `It has been foundfthat when the `process iscarriedout fin this temperature range the Chydrogenation and aromatization reactions 'arebo'tli rapid such that control of the "temperature `profile becomes possible. Furthermore, lcarbon deposition on the-catalyst isnot excessive anddestructive hydrogenation of naphthenes andother feed stock components such as destroys hydrogen-producing naphthenesfand needlessly consumeshydrogen is minimized.

The pro'cesslmay` be carried' out at-preSSures'between about atmospheric and `1000 pis. i. and preferably in the range-of about 200 to 60011. s, i. Such pressures promote the hydrogenaticn fof olefins and the `simultaneous dehydrogenation cf naphthenes to aromatics,

The hydrogen produced in the `process Tis continuously recirculated with the incoming feed and at-intermediate levels in the moving cat' bed if desired. In general the hydrogen recycle rate should be maintainedbetwe'en about 100 and 10,000 cubic feet of hydrogen per barrelof fee-:l and Ypreferably inthe range of about 500 to 1500 cubic feet per barrel of feed. "Ihe 'hydrogen conn centration of the recycle gas will normally `vary between 25 and '70% by -volume is generally inthe range of about 50% by volume.

`The liquid hourly space `velocity which relates the volume of liquid feed to the volume of the catalyst 'bedwhich is'contaoted per hour may in the range of 0.1 to 10 `and preferably in `the range of 0.2 to 1.5. Where `the feed stoel; is injected at intermediate levels in the reaction zone the liquid hourly space velocity for the purposes of this invention is calculated as though the `entire amount of liquid feedwerepassed throughout the entire catalystbed.

In a moving bed type catalytic process thereaction zon'e is continuously lled from the top with fresh catalyst and spent catalyst is 'continuouslywithdrawn frornthe bottom. The average time requiredv to replace the entire reactor volume with fresh catalyst is defined as the catalyst contacttime. The catalyst contact time may alternatively be dened as the time during which a given catalyst particle on the average is contacted with reactants between regenerations. vln general it has been found that the catalyst contact time should be between about 0.5 and'100 or more hours and preferably in the range of about 5 to 30 hours.

The process and apparatus of the presentinvention will be'more clearly understood by referenceto the accompanying drawings in which:

Figure l is a schematic flow diagram of a moving bed catalytic process wherein two feed stocks are employed to obtain a desired temperature profile within the reaction Zone and whereinthe reaction zone is positioned over theregeneration zone.

Figure 2 shows a modification of the apparatus of Figure 1 wherein the regeneration zone is positioned above the reaction Zone.

Figure `3 shows an electrical resistance circuit for controlling the flow rate of one feed stock in relation to the continuously varying iovvrate of a second feed stock such that the sum of the two flow rates remains constant.

Figure 4 shows an alternate method for controlling the flow rate of one of two feed stocks by va process variable and controlling the flow rate of a second feed stock to provide a constant total reactor feed flow.

Figure compares the temperature profile of a moving bed reaction zone when cracked feed is injected at three bed levels with the profile obtained where both straight run and cracked feeds are injected at a single level.

Figure 6 compares the temperature profile of a moving bed reactor when the recycle hydrogen is injected at three bed levels with that obtained where all of the recycle hydrogen is injected with the feed stock.

Figure '1 shows three methods for controlling the hydrogen recycle stream while simultaneously controlling the blend of the two feed stocks flowing to the reactor.

Referring now more particularly to Figure l, straight run feed stock is introduced into line II and heated by heater I2 whence it flows through line I3 to motor valve I4. Motor valve I4 is controlled according to methods to be described hereinafter. Flow from motor valve I4 passes through line I5 to reactor feed inlet I6 and thence into primary feed engaging zone I1.

Cracked feed stock `is introduced through line to heater 2 I and flows through line 22 to motor valve 23. Motor valve 23 is controlled by a suitable process variable described more fully hereinafter such as by the reactor pressure, the hydrogen content of the hydrogen recycle stream or other such variable. If desired, effluent cracked feed stock from motor valve 23 may be passed into line 24 through opened valve 25 and line 26 whence it joins the straight run feed stock in line I5 flowing to reactor feed inlet I6.

Alternatively Valve is blocked and effluent cracked feed stock from motor valve 23 ows through line 21, opened valve 28 and line 29 to header line 30.

Header line 30 is connected to a series of four motor valves 3l, 32, 33 and 34, respectively. Effluent from motor valve 3| flows through line to reactor feed inlet I6 wherein it is mixed with the straight run feed flowing through line I5. EITluent from motor valve 32 flows through line 36 to feed inlet 31 which in turn connects with secondary feed engaging zone 38. Motor valve 33 effluent flows through line 39 to feed inlet 40 which connects with tertiary feed engaging Zone 4I. Motor valve 34 effluent flows through line 42 to feed inlet 43 which connects with quaternary feed engaging zone 44.

Flow through motor valve 3l is controlled by temperature recorder controller 45 which is actuated by a thermocouple located in primary reaction zone 46. Flow through motor valve 32 is controlled by temperature recorder controller 41 which is actuated by a thermocouple located in secondary reaction Zone 48. Flow through motor valve 33 is controlled by temperature recorder controller 49 which is in turn actuated by a thermocouple located in tertiary reaction Zone 50. Flow through motor valve 34 is controlled by temperature recorder controller 5I which is in turn actuated by a thermocouplelocated in quaternary reaction zone 52.

I-Iot recycle hydrogen flowing in line 66 enters line 6I, open valve 62 and line 63 whence it flows to reactor inlet I6 and thence into primary feed engaging Zone I1.

The mixture of straight run feed, cracked feed and recycle hydrogen in primary feed engaging zone I1 pass into contact with freshly regenerated and reduced catalyst in primary reaction zone 46 which is supplied through catalyst transfer line 64. In the presence of the catalyst a part of the naphthenes are endothermically aromatized and a part of the oleilns are exotherrnically hydrogenated. The relative rates of these two principal reactions accordingly raise or lower the temperature of the catalyst and vapors flowing through primary reaction zone 46. The thermocouple in primary reaction Zone 46 transmits temperature fluctuations of the primary reaction Zone to temperature recorder controller 45 which in turn opens motor valve 3| in order to increase the temperature or closes motor valve 3I in order to lower the temperature as required.

Catalyst and vapors from primary reaction zone 46 flow to secondary reaction zone 48 through secondary feed engaging zone 38. Secondary feed engaging zone 38 comprises a transverse plate 65 which is fitted with a series of downcomers 66 which transfer catalyst from the primary reaction Zone 46 above plate 65 to secondary reaction zone 48 thereby providing a free vapor space for introducing vapors into uniform contact with the catalyst in the secondary feed engaging zone 38.

Catalyst and vapors issuing from downcomers 66 are enriched with additional cracked feed stock introduced into secondary feed engaging zone 38. In secondary reaction zone 48 the freshly added olens are at least partially hydrogenated to furnish heat while naphthenes are simultaneously dehydrogenated with the consumption of heat. The thermocouple in secondary reaction Zone 48 transmits temperature fluctuations to temperature recorder controller 41 which in turn opens or closes motor valve 32 to permit temperature control.

In corresponding manner catalyst and vapors from secondary reaction zone 48 are discharged to tertiary reaction zone 5I! through tertiary feed engaging zone 4I wherein they are enriched with additional cracked stock through motor valve 33 controlled by temperature recorder controller 49 to maintain temperature control in tertiary reaction zone 50.

Likewise catalyst and vapors from tertiary reaction zone 58 pass through Quaternary feed engaging zone 44 to quaternary reaction zone 52 wherein they are enriched with additional cracked stock through motor valve 34 controlled by ternperature recorder controller 5I to maintain temperature contro1 within the quaternary reaction zone 52.

Products from quaternary reaction Zone 52 and catalyst flow through product disengaging Zone 6-1 which, like the previously described feed engaging zones, consists of a transverse plate 68 and a series of downcomers 69 which discharge catalyst through plate 63 to a short distance therebelow. Gases separating from the flowing catalyst are removed in the gaseous space thereabove through outlet 1I) and line 1 I.

Product vapors in line 1I flow through cooler 'I2 wherein the vapors are condensed and these flow through line 13 to gas-liquid separating vessel 14 fitted with liquid level control 15. Accumulated liquid in vessel 14 is removed through lower line 15 which is in turn controlled by motor valve 11. Motor valve 11 is actuated by liquid level control 15 to maintain a given liquid level in vessel 14. Eiliuent from motor valve 11 flows through line 18 and orifice plate 19 tov line 80 whence it flows to refined product production. Orice plate 'I9factuates iiow recorder controller 8| which is the controlinstrument for motor valve I4 on the straight run feed line. Motor valve I 4 is thus controlled to increase or decrease the flow of straight run feed to the primary reaction zone 45 in order to supply a given product flow rate to line Gaseous reaction products are withdrawn from gas-liquid separating vessel I4 through line Pressure on line 85 aetuates pressure recorder controller 86 which in turn controls motor valve 23 on the cracked feed stock inlet line. As the supply of cracked feed stock increases beyond a desired value, additional hydrogen is consumed and the system pressure, as determined by pressure recorder controller 36, falls correspondingly. The

drop in pressure in turn partially closes motor valve 23 to cut back on the cracked feed stock and decrease hydrogen consumption and thus permit the pressure to rise to a pre-set value. Similarly, whenever the cracked feed stock is insufficient the system pressure will rise above the preset value and motor valve 23 will be correspondingly opened.

The opening and closing of motor valve 23 ultimately increases or decreases the flow of reiined production through orifice plate 19. Flow recorder control BI operating on orifice plate 'I9 in turn opens or closes motor valve I4 on the straight run feed inlet in order to maintain a constant Iiow of product. The net result of such instrumentation is to provide approximately a constant total flow of the straight run feed plus the cracked feed owing to the several reaction zones,

The gaseous product withdrawn from separating vessel 'I4 through line 85 may be processed if desired to separate hydrogen sulfide and ammonia. If such operation is desired valve 8l is opened to permit the now of gas through line t3 to absorber 89 wherein the gas countercurrently contacts a suitable absorbent for such gases such as mono-ethanolamine, di-ethanolarnine or the ire. The rich absorbent from absorber 89 is withdrawn through line S0 and passed through stripper 0I wherein the solution is heated so as to flash aby sorbed gases overhead through line 92. Lean absorbent solution is withdrawn through line whence it hows to pump 93 and is forced through line 94, cooler 95 and line 96 to the top of absorber B9.

Non-absorbed gases containing hydrogen are withdrawn from absorber 89 through line 91. Where ammonia and/or hydrogen sulfide removal `is not required, or is not desirable, valve 85d is opened and the gases from gas-liquid separating vessel I4 are passed through line 85h to line Sl, thereby by-passing the absorber. A part of the stream in line SII may be discharged continuously through valve 98, oriiice platela and line 59 into fuel gas line |00. A constant bleed of hydrogen-containing gases from the system prevents the accumulation of inerts in the stream such as methane, ethane and the like. Valve 9S may, if desired, be a motor valve which is in turn controlled by a flow recorder controller 98h in line 539 which is in turn responsive to variation of flow through orifice plate 90d. Alternatively, a part of the gas stream in line @l may be processed to recover the hydrogen content which is then returned to line 97 downstreamwardly and the inerts may be discharged to fuel gas. The major from stripper 9| 1I)` Pressured gas from blower I 0I passes through line I02,jheat,er |03 into line 60 previously described as the. recycle hydrogen stream.

Spent catalyst from product disengaging zone G'I passes downwardly through stripping zone |04 wherein it flows counter-currently to upwardly flowing hydrogen introduced from line 60 through valve |05 and line |00. The hydrogen flows upwardly through stripping zone |04 and is withdrawn along with the products through line 1I. Stripped catalyst fdows downwardly from stripping cone |04 `through sealing Zone |0511.. Steam in line IIE is introduced into steam engaging zone |01 wherein a part flows upwardly through downcorners Ilia and sweeps the downi'lowing catalyst free of hydrogen. The upwardly moving steam passes through stripping zone |04 and is removed along with hydrogen and other products. A portion of the steam entering line IIO passes downwardly with the catalystl and flows into regeneration zone I de. Compressed air or air diluted with inert. gas such as flue gas or nitrogen is injected through line I I I into` air engaging zone I I2 whence it hows downwardly with the catalyst through regeneration zone |09. The burning of the carbcnaceous deposits from the catalyst in regeneration zone |09 is controlled to a temperature below that which causes thermal decomposition of the catalyst. Such regenerations may be controlled to` temperatures below 1100 F., for exam- Dle. This may be done either by diluting the air with inert gas or by indirectly cooling the hot catalyst with acooling agent circulated through pipes or otherwise such as is shown diagrammatically in regeneration zone |09. Regenerated catalyst and iiue gases iiow into regeneration gas disengaging zone IIZ whence they are removed through line. I I3.

Regenerated catalyst thereafter ows through sealing :one IIit. Steam introduced through line I I5, iiows into steam engaging zone I I6 wherein it divides and a part flows upwardly through downcomers I I1 and is removed from the regeneration gas clisengaging zone through line IIJ-i. The remaining steam ilow passes, downwardly with the catalyst and prevents an uplow of hydrogen into the regeneration zone |09.

Catalystfrom sealingr zone II4 nows to pressuring zone I I8 through line IIS. Pressuring zone H3 is any suitable form of apparatus for removing catalyst from line II9 increasing its pressure and transferring the pressured catalyst to line IZ. Pressuring zone I I8 may be `a star feeder such asis employed to transfer solids from one pressure to a different pressure. In another modiication pressuring zone I I3 may consist of a series of vessels each of which may alternately be employed to receive a solid at a rst pressure, such as by means of gravity flow, after which the Vessel is isolated, pressured, and connected with I the high pressure line to permit removal of the portion of the hydrogen-containing gas in line fil passes to blower I0! wherein its pressure is increased suflicientlyto overcome its resistance to `fiow through the multiple reaction zones, etc.

solids, such as by gravity, into the higher pressure Zone.

Catalyst flows from pressuring zone I lo through `transferring Zone created by line I 20 into the inductionzone bounded by closed vessel I 2l Recycle hydrogen in line 9'! is withdrawn through line i522 into compressor whence it is compressed to somewhat above the lift line pressure and passed through line |24, valve |25 and line I 26, heater I2I, line |25 into inlet |29 of closed vessel I2I.

The compressed hydrogen in vessel I2! exerts a downward pressure on the catalyst surface partially lling the vessel and causes such catalyst to 1l enter the lower open submerged end of lift line i3@` whence the catalyst is forced upwardly through. the bore of lift line |30. The flow of catalyst in lift line |30 is preferably of the compact type known as mass flow.

Following the oxidation in the regeneration zone |89 the catalyst must normally be reducedA prior to re-using it in a reaction zone. In this. modification of the invention the oxidized cata-- lyst is lifted with hydrogen and the catalyst is re duced during the lifting.

The solid bed of catalyst in lift line ld presses'` upwardly against pressure plate |3| and spills downwardly therefrom in a compact separation zone |32. Reduced catalyst from separation zone |32 flows through transfer line liti and discharges: into primary reaction zone 46 wherein it contacts straight run feed stock and hydrogen as described hereinbefore.

As has been previously described, the entire flow of cracked feed stock may be introduced through line l along with the straight run feed stock by opening valve and closing valve 28. Under such conditions the temperature control within the reactor may be obtained by varying the hydrogen content of the gaseous phase` throughout the several reaction zones. The variations in the concentration of the hydrogen may be pro-` duced by completely closing valve 62 and opening valve |35 whereupon recycle hydrogen is transferred from line 541 to header line 30 which is in turn attached to motor valves 3|, 32, 33 and 34, for the introduction of hydrogen in the primary, secondary, tertiary and quaternary reaction zones' 46, 48, 5S and 52 respectively. The flow through each motor valve under this type of operation is controlled to maintain a desired temperature profile analogous to that which has been described hereinbefore in connection with the cracked feed injection. As the temperature in a given reaction zone increases, the hydrogen injection in the engaging zone corresponding thereto is decreased to maintain a pre-set temperature. As the temperature decreases in a given reaction zone the hydrogen injection in the corresponding engaging zone is increased.

Under normal operation the ratio of cracked and straight run feed stock is so regulated that a hydrogen balance is maintained within the reactor system, and this is the preferred method of operation. However, in certain cases hydrogen produced externally or arising from miscellaneous renery operations such as cracking may be introduced into the system through line l, valve |31 and line ld whence it flows into hydrogen recycle line (i0. Such hydrogen may be heated as required by means not shown.

In still another modification of the invention a mixture of cracked stock and hydrogen may be passed to header line 30 by the opening of valves 28 and |35 and the flow of the mixture to each of the four reaction zones may be controlled by motor valves analogous to that previously described for `either of the single components.

Referring now more particularly to Figure 2, the reducing and regenerating sections of the apparatus may be placed over the several reaction zones and coked rather than regenerated catalyst may be transferred to the lift line. Also the catalyst flow may be countercurrent to the flow of vapors.

In Figure 2 straight run feed stock is introduced through line |49 whence it flows through heater 14|, line |42 and motor valve |43. Effluent from motor valve |43 flows through line |44 to primary feed engaging zone |45. Hydrogen flowing inline |56- joins line |44 and passes into the primary' line |44 wherein it joins the straight run feed.

stock. Alternatively efliuent of motor valve |5 passes through valve |52 into line |53 whence it flows into header line |514. Analogous to the valving arrangement and temperature control described hereinbefore in connection with Figure 1, header line |54 discharges into a series of four motor valves` |55, |56, |51 and |58,=each `of which in turn controls the flow of cracked feed stock in header line |54 to primary feed engaging zone |1115, secondary feed engaging zone |59, tertiary feed engaging Zone Hill and Quaternary feed engaging zone |5|, respectively. The flow in each of the four motor valves |55, |56, |51 and |58 is controlled by four corresponding temperature recorder controllers |62, H53, Iil and |65, respectively, which in turn are actuated by four corresponding thermocouples in the four reaction zones, viz., the primary reaction zone |66, the secondary reaction zone |51, the tertiary reaction zone |68 and the Quaternary reaction zone |59. Hydrocarbon vapors and hydrogen, in primary feed engaging Zone |115, contact countercurrently the descending catalyst and flow upwardly through downcorners against the downward flow of catalyst. Such vapors pass into contact with the primary reaction Zone Iii-ii wherein a partial reaction occurs. rThe vapors leaving primary reaction zone ld mixes with additional cracked feed stock in secondary feed engaging Zone |59 and pass upwardly through downcomers into secondary reaction Zone |51. The partially reacted vapors from secondary reaction Zone |51 are mixed with additional cracked feed stock and pass upwardly into the tertiary reaction Zone |58 and after reaction are mixed with additional cracked feed stock .and pass upwardly into the Quaternary reaction zone |69. The reaction products separate in product disengaging Zone |10 and are withdrawn through line |1| and pass through cooler |12 to gas-liquid separating vessel |13. Liquid withdrawal from the bottom of gas-liquid separating vessel |13 is controlled by motor valve |14 which is actuated by liquid level control |15. The nal product is withdrawn through line |16. Hydrogen-containing gases` are withdrawn from the top of gas-liquid separating vessel |13 through line |11 which is fitted withhydrogen ,analyzer controller |18. Line |11 is also attached to line |19 which passes to motor valve operated by back-pressure controller |3| operating to maintain a given pressure in line |19. Make gas is withdrawn as the eiiluent from motor valve ltll through line |182. The bulk of the hydrogen stream in line |11 passes through valve |83 to blower |34 whence it flows to heater |85 and is discharged into line |85. Hydrogen in line flows through valve itl into line |46 previously described.

The hydrogen content of the make gas discharged through line |82 may be recovered by any suitable separation process, such as fractional distillation, hypersorption, oil absorption or the like, and returned to the system such as through hydrogen feed line |88.

While the preferred method of operation is such that the hydrogen produced balances the creased correspondingly.

aecaeai 13 hydrogen consumed-in the process; outside hy-V drogen may be introduced through line |88 and valve |89 whence it flows intoV line |86.

Spent catalyst from primary feed engaging zone |45 flows downwardly through sealing zone 5 |99, which is similar to sealing zones described hereinbefore in connection with Figure 1. A portion of the sealing steam flows upwardly and passes through the several reaction zones with the hydrocarbon feed stock. Another portion of the sealing steam flows downwardly through pressuring zone |9| which is similar to that described hereinbefore in connection with Figure l. Spent catalyst, after it has been repressured in pressuring Zone |9|, flows through transfer line |92 into induction zone |93. Flue gas or flue gas air mixtures are introduced under pressure through line |9ll into the induction zone |93 and exerts a downward presf'lre on the bed of spent catalyst contained therein, causing it to flow into the submerged lower end conveyance line |95 and upwardly therethrough. The compact bed of catalyst flowing. in conveyance line |95 flows upwardly and fills cylinder |96.. C'atalyst flows from the bottom of cylinder |96 in a compact bed into lift gas separation zone |9l wherein the liftgas separates and is removed through line |9'|a.

In one modification of the invention, all or part of the regeneration of the spent catalyst may be effected during conveyance of the spent catalyst in conveyance line |95. Under such conditions temperature control of the catalyst is effected by control of the carbon on the catalyst and by the concentrationof the air added to the lifting gas.

C'atalyst from separation zone |91 flows downwardly through regeneration zone |98 which contains indirect cooling means shown diagrammatically.` In regeneration zone |93k the spent catalyst countercurrently contacts regeneration gas such as air or mixtures of air and` inert gases which are introducedzintor regeneration gas engaging zone |99. Catalyst from the `regeneration Zone |93 flows through. sealing Zone 209 4.5'

wherein `a small amount of steam passescountercurrently through the regeneratedcatalyst'and a secondportion of the steam passesrconcurrently with the catalystdownwardly. The upward flowing steam is removed in the flue gasA disengaging zone |97. Catalyst from sealingzone 2|l|1 flows concurrently withLsteam into-reducing gas engaging zone 29|.

Hydrogen from. line llcis permitted to flow from line 202 through Valve 293 and line 294 into. reducing gas engaging Zone 29|. Hydrogen gas flowing through catalyst reduction Zone\2.95'reduces the catalyst and the spent reducing gas and catalyst iiow downwardly and are discharged` into thel product disengaging zone lill. The catalyst continues to iiow downwardly through the four reaction zones described hereinbefore and the spent reducing gas is-removed with the products through line lll.

It ispreferable that the total feed rate tothef reaction zones, Which in turn is .the sumofthe flow rates of the straight run and cracked feed stocks, be maintained constant.

Hydrogen analyzer controller |28 operates to control the motor valve |99A on thecracaed feed. inlet in order to maintain a fixed concentration of hydrogen in the recycle gas stream. As the hydrogen concentration increases .or decreases the flow of cracked stock` is increased or` de- Referring now,V more particularly tolFigureaS in connection with FigureZ, Figure 3 presents an electricaly system `for maintaining a` constant feed rate to the reactor. In Figure 3, F? corresponds to the desired totalflow rate and a pointer "c is set, on anelectrical resistanceata point corresponding to the total flow desired. Thisfis determined by letting` 1 ohm of resistance be, say, X barrels of feed. The flow of crackedfeed stock Fc is measured by anoriflce plate |49 and the magnitude of such flow rate, translated into resistance, is continuously set on the electrical resistance by pointer im The flow rate of the straight run feedstock Fsr corresponds therefore to theportion of the resistance corresponding `to E which remains unmatched by Fc. Accordingly, in Figure 2, motor valve |43 is controlled by instrument 2li) which is` of the type showninlligure 3 or a pneumatic equivalent and which continuously maintains the electrical or other relationship shown in Figure 3.

Referring now` more particularly to Figure 4, it often happens that thestraight run andcracked feed stocks are introduced through a single inlet into al reaction zone,. such as Where the hydrogen injection isA employed to control` the temperature profile of the reactor. An arrangement for controlling the feed4 rates for this type of operationis shown inFigureA; Feed stock A is introduced through motortvalvev 220- and line 22| into surge vessel 222-. Feedstock B is introduced throughmotor valve 22.3- and line 224 into surge vessel 222. Motor valve 223 is controlled by a suitable process variable such as pressure, hydrogen concentration or the like.` Surge vessel222 is iittedwith liquid level control 225 which in turn actuates `motor valve 229. Surge vessel 222' is discharged through line 225 and pump` 221 through orifice plate 2219 which operates flow recorder control 229, to maintain by control of pump 227 a constant flow rate through line, 23.

By the method of control in Figure 4 a constant flow rate through line 239 of the reactor'A feed is maintained. The flow` rate of feed stock B through line 224 is controlled` by any suitable process variable. Whatever the feed rate of eed` stool; B with relationship to the required reactor feed, liquid lever control 225 operates motor valve 22|) to maintain a given level in surge vessel 222; Thus the sum of the flow rates of feed stock Aand` feed stock B is maintained constant while the one may be varied by a suitable process control.

While the lratio of thevstraight run feed to the cracked feed required to maintain temperature control and` hydrogen balance varies with the instantaneous composition of both feed streams, it has been found that for typical cracked distillates and straight run distillates, a balance is usually obtained in the vicinity of 30 volume per cent of straight run and '70` Volume per cent of cracked stock. Generally the straight run requirement may vary between about l5 and 59 volume per cent and the cracked requirement willbe between about 85 and 50 volume per cent correspondingly. The ratio of straight run feed to cracked feed will normally be between about 0.2and 1.0.

Itis thus apparent that in broad aspect the flow rate of two feeds, the one cracked and the other straight run, may be so controlled by the methodof this invention that the flow rate of the one feed may be controlled to give a given hydrogen concentration in the hydrogen recycle gasto give a given hydrogen production or consumption, to maintain a given pressure in the recycle gas system or the like while the iiow rate of the other may be controlled to maintain a constant ow of feed to the reactor or to maintain a constant flow of liquid product from the reactor. This method of feed control may be applied to other types of reactors than the moving bed type such as to either iiuid or static reactors.

As has been described in connection with Figure 1, a pressure recorder controller 36 operating from the line 85 which carries the gas separated in gas-liquid separator Hi may be employed to vary the ow rate of the cracked feed stock so as to maintain a given set of pressures throughout the reactor system. It is apparent that pressure recorder controller 86 could be employed to operate motor valve I4 controlling the straight run feed stock with the cracked feed stock being in turn controlled to provide a given total volumetric flow to the reactor.

A broader method of employing pressure control to Vary the ratio of the straight run to cracked feed stock is shown in Figure '7.

Referring more particularly to Figure 7, gas from gas-liquid separator (for example, gas-liquid separator 'i4 in Figure 1) ilows upwardly through line 250 and enters the recycle gas system (for example, blower l! of Figure 1). Pressure recorder controller 25l is attached to line 255 and is in turn employed to regulate motor valve 252 which is employed to control the flow of straight run feed such as is performed by motor valve I 4 of Figure 1. Make gas from line 250 flows through orifice plate 253 and motor valve 254 into line 255 whence it flows to a suitable storage means not shown or to a second reactor system not shown for hydrogenating hydrocarbon fractions, or otherwise utilized. The control to motor valve 254 is connected to three-way switch 256 which connects to terminals described hereinafter.

Flow recorder controlled 257 is actuated by orifice plate 253 and may be employed by suitable switching of switch 255 to actuate motor valve 254. This modification of the invention may be employed to maintain a constant flow through orifice plate 253 thereby giving a constant flow rate of hydrogen-rich gas. Under these conditions a constant ow rate of make gas is removed from line 255 and the pressure in line 255 is maintained through the action of pressure recorder controller 25E which opens motor valve 252 to permit a greater ow of straight run feed stock and thereby increase the hydrogen make or, alternatively, to close olf on motor valve 252 in order to decrease the hydrogen make as required.

Hydrogen analyzer controller 255 is fitted to line 250 and continuously analyzes the gas stream flow therethrough. Hydrogen analyzer controller 258 may be employed by a suitable switching of switch 255 but employed to control motor valve 254. Under these conditions a suitable concentration of hydrogen may be maintained in line 250. When the hydrogen content of the gas stream in line 250 falls below a predetermined value motor valve 254 opens to bleed lean hydrogen from the system. This bleeding in turn causes a reduction in pressure which in turn actuates pressure recorder controller 25| and causes the opening of motor valve 252 to increase the flow of straight run feed stock so as to increase the hydrogen content of the make gas.

Pressure recorder controller 259 may be athydrogen feed gas to the second hydrogenation p system. Thus the make gas from the apparatus of Figure 1 may be employed for hydrogenating any desired petroleum fraction. A pressure plug in the second hydrogenation reactor is connected to pressure recorder controller 255 which in turn may be connected through a suitable switching of switch 255 to motor valve 255. As the hydrogen requirement of the second hydrogenation reactor system rises or falls motor valve 251i opens or closes in order to meet such requirements. The changes in pressure in line 250 accordingly actuate pressure recorder controller 25! which in turn opens or closes motor valve 252 in order to increase or decrease the ow of straight run feed in order to increase or decrease the hydrogen make gas. v

The apparatus of Figure '7 may be employed in connection with apparatus of the temperature control modification of this invention or with the modification wherein the hydrogen, cracked feed stock and straight run feed stock are introduced in a single reactor inlet.

Perhaps the application of this invention can best be understood by reference to the following specic examples.

Example I A mixture of 30% straight run gasoline and r70% coker pressure distillate, both having a boiling range of about .to 400 F. is supplied to a xed bed type reactor. The reactor is lled with a cobalt molybdate type catalyst containing about 2% by weight of CoO and about 10% by weight 0f M003 supported on a carrier consisting essentially of 5% Sim-95% A1203 in coprecipitated form. The catalyst was prepared by first impregnating the dried carrier with an aqueous cobalt nitrate solution, calcining at 600 C., impregnating with an ammoniacal ammonium molybdate solution and calcining at 600 C.

About 1500 ou. ft. of 60% hydrogen-40% methane is employed as recycle hydrogen and the reaction is carried out at a pressure of about 400 p. s. i. The liquid hourly space Velocity is 1.0. The product obtained thereby has about 0.10% by Weight of sulfur and contains about 30% by volume of aromatics. The temperature profile of the reactor is shown as the broken curve labeled M in Figures 5 and 6.

Example I I The work of Example I is repeated but with the changes that a moving catalyst bed is employed and only one-third of the coker distillate is introduced with the straight run gasoline while an additional one-third is introduced 33% down the reactor bed and the remaining one-third at 66% down the reactor bed. The product obtained thereby has about 0.03% by weight of sulfur and contains about 50% by volume of aromatics.

The temperature prole of the reactor bed is shown in Figure 5 by curve N and the concentration of olefins and thiophenes remaining unreacted (including the amounts added) is shown by curve 0.

Example III The work of Example I is repeated but with the changes that a moving catalyst bed is ernployed and only 300 cu. ft. of hydrogen per barfrel of feed areintroduced with themixture fof coker pressure distillateandfstraight runi gasoline and 500 cu. ift. per barrel fOffeed are introduced 33 rldownth'e'reactorlbed aridJSOO fare introduced 66% down the reactorbed. rlheprcduct obtained thereby contains 'about 003% by weight-lof sulfur and about '50% Iby i-volume "of aromatica The temperature profile of theireator -bed is Ashown in Figure 16 'by solid curve P `while the amount of i hydrogen added per fbarre'l Eisfshovlfn by curve "Q. f

ExamplelrIlV WhenV Example Il'zis repeate'd `with ithe `vexception that countercurrent -ilowof catalyst (heated to 1050 Fsprior tointroduction) :'sfempl'oyed and the relative distribution of the coker pressure distillatestream between ithe three-finlets1at`0%, v33% and 66% upthe reactorfbed isfautomatically controlled tof-maintain' the three partsfiof lthe bed` 'at nearlyuniform temperature, l a further improvement of ipro'duct yduality lresults as y'indicated by the increased aromatic content.

It is. apparent ffrom the foregoing 'examples Eof this invention` that close temperaturefcontrol results 1in high product quality. Such temperature control lmay be `'ob'taine'cl bycontrol `of.1th`e`c'omposition of the mixedlfeedfsupplied Ato the 4reactor or Ipreferably lby control of` lthe' concentration of the oleiins or of the recycle fhydrogen throughout the reactor bed.

While theadvanges "of temperature 'control have been priniarily-izln-iscribed as those resulting in greater aromatic synthesis, it has also been found that the liquid recovery is Yalso a function ofclose temperaturewcontrol. AThe liquid recovery drops oi rapidly as the temperature `increases due to the'lsplitting ofthe hydrocarbons land hydrogenation of the fragments. (As the temperature increases above about 925th'. and especially above about 950 F., the hydrocracking increases the production of gas, such as methane, and decreases the liquid recovery. At temperatures in the range of 800 F. to about 900 F. hydrocracking tends to increase the liquid recovery by the production of two hydrocarbon molecules from one hydrocarbon molecule with the lighter products being less dense. Thus temperature control affords a means for controlling the liquid recovery and maintaining it at a maximum for a given product conversion.

Throughout this specification the term hydrogenatable hydrocarbon feed stock is used to denote a mixture of hydrogenatable compounds and hydrocarbons and dehydrogenatable hydrocarbon feed stock denotes a mixture of dehydrogenatable compounds and hydrocarbons. Thus a mixture of sulfur compounds and hydrocarbons would be a hydrogenatable hydrocarbon feed stock. Furthermore, a reaction zone may correspond to a single reaction zone, i. e., a primary reaction zone, or it may be a series of such reaction zones.

The foregoing disclosure of our invention is not to be considered as limiting since many variations may be made by those skilled in the art without departing from the spirit or scope of the following claims.

We claim:

1. A process for the conversion of hydrocarbons which comprises passing a hydrogenatable hydrocarbon feed stock, a dehydrogenatable hydrocarbon feed stock and hydrogen into a reaction zone, said reaction zone containing a continuously replenished bed of a carrier-supported ELl() cobaltimolybdate catalyst, maintaining yconditions in 'said reaction zone' which` cause said hydrogena'table 4hydrocarbon feedstock to be hydrogenated and said dehydrogenatable hydrocarbon` feed stock to be dehydrogenated, 4continuously controlling the relative concentrations of hydrogen, .hydrogenatable rhydrocarbon feed stock and ldehydrogenatable hydrocarbon feed stock inisaidrreaction zone by injecting at least part-'ofatlleast'one offsaidreactan'ts at aplurality ofipoi'ntsalong 'said reaction Zone, so as to decrease ftemperature changes through the reactionz'one and withdrawing products from said reaction zone.

#2. Alprocess according to "claim 1 wherein the volumetric ratio of 'dehydrogenatable hydrocarbon feed stock to v.hydrogenatable hydrocarbon feed stock vis controlled between about 0.2 and L0 and the temperatures `changes 'throughout said `reaction zone donot exceed 20 F.

`3. yA processffor the catalytic conversion of hydrocarbondistillates A*which 'comprises introducing lone reactantlslected fromlthe class consisting of yhydrogen and a. cracked distillate into a reactionzone'through alplurality of inlets, the amounts fof said :one Areactant .injected at each inlet being controlled lby'a process variable in such manner as to minimize temperature fluctuations throughfsaid reaction zone, said inlets being located at a plurality `of points along the vapor .flow through .said 'reaction szone, introducing a straightrun distillate 'and'the-other of :said reactants fthrough :an inlet -whiohflis upstreamward` with respect 4to 's'aid'zvapor fiowthrough said reaction vzone, continuouslyfpafssing a solid carner-supported cobalt-molybdate catalyst into and through Isaid reaction hone, withdrawing products from said .reaction Vzone, withdrawing vspent catalyst from said reactionfzone,regenerating saidspent catalyst, and 'continuously returning the regeneratedcatal-ystftofsaid `reaction zone.

4. A process according to claim 3 wherein the reactant injected into said plurality of inlets is hydrogen.

5. A process according to claim 3 wherein the reactant injected into said plurality of inlets is said cracked distillate.

6. A p-rocess according to claim 3 wherein the volumetric ratio of straight run distillate to cracked distillate is controlled to between about 0.2 and 1.0.

'7. A process for conjointly reforming a naphthenic straight-run hydrocarbon stock and a cracked hydrocarbon stock each boiling below about 450 F., which process comprises flowing an active reforming-dehydrogenation catalyst comprising as an essential active ingredient an oxide of a metal selected from the group consisting of vanadium, chromium, molybdenum and tungsten in the form of a granular substantially compact bed through a plurality of alternating gas engaging zones and reaction Zones, said gas engaging zones being substantially devoid of catalyst, passing said straight-run stock into a rst engaging zone, passing at least a part of said cracked stock and at least a part of recycle hydrogen steam into said first engaging zone, nowing said straight-run stock, said cracked stock and said recycle hydrogen stream from said rst engaging Zone into a first reaction zone and effecting therein endothermic conversion and aromatization of said straight-run stock and exothermic conversion and hydrogenation of said cracked stock, regulating the relative concentrations of cracked stock and hydrogen in said 'rst engaging zone by a means responsive to the temperature o said first reaction zone, passing products from said first reaction `zone through a subsequent engaging zone into a subsequent reaction zone, regulating the relative concentrations of cracked stock and hydrogen in said subsequent engaging zone by adding further quantities of one of the reactants selected from the group consisting of cracked stock and hydrogen, said addition of reactant in said subsequent engaging Zone being controlled by a means responsive toithe temperature of said subsequent reaction zone,` passing the products from the last of said reaction zones to a product disengaging zone and separating products from catalyst therein, separating a recycle hydrogen stream from said products and returning at least a part of said recycle hydrogen stream to said rst engaging zone, the total volumetric ratio of straight-run to cracked stock in said process being vcontrolled between about 0.2 and 1.0, the temperatures throughout said plurality of re action zones being controlled within the range of about`850 and 900 F., the variation from the lowest to the highest of said temperatures not exceeding about 20 F. and the pressure in said reaction zones being between about 200 p. s. i. and 600 p. s. i.

8. A process according to claim '7 wherein the said catalyst is of` the cobalt molybdate type.

9. A process according to claim '7 wherein the spent catalyst separated from the series of reaction zoneslowsby gravity through a stripping zone, a pressuring zone, and into an induction Zone and is lifted in a lifting zone to a separation zone wherein it is separated from the lift gas and flows by gravity through a regeneration zone, a sealing zone, and a reduction zone into said series of reaction zones.

10. A process according to claim 7 wherein the spent catalyst separated from the series oi reaction zones flows through a stripping zone, a sealing zone, a regeneration zone and through a pressuring zone into an induction zone, whence it is lifted with a hydrogen containing lift gas through a lifting zone and is simultaneously reduced and is then passed into a separation zone to separate the lift gas and flows to said series of reaction zones.

11. A process according to kclaim 7 wherein the flow rate of the one of the two stocks into said rst engaging zone is controlled by va means re sponsive to the variations of a process variable and the flow rate of the other of said two stocks into said first engaging zone is controlled by a means responsive to the iiow rate of said products after said separating of said recycle hydrogen stream.

12. A process according to claim '7 wherein the flow rate of the one of the two stocks into said rst engaging zone is controlled by a means responsive to the variations of a process variable and the flow rate of the other of said two stocks into said first engaging zone is controlled by a means responsive to the iiow rate of the first of said two stocks.

13. A process according to claim 11 wherein said process variable is the pressure of said recycle hydrogen stream and at least a part of said hydrogen recycle stream is removed from the system.

I References Cited in the le of this patent UNITED STATES PATENTS Jonson Nov. '7, 

1. A PROCESS FOR THE CONVERSION OF HYDROCARBONS WHICH COMPRISES PASSING A HYDROGENATABLE HYDORCARBON FEED STOCK, A DEHYDROGENATABLE HYDROCARBON FEED STOCK AND HYDROGEN INTO A REACTION ZONE, SAID REACTION REACTION ZONE CONTAINING A CONTINUOUSLY REPLENISHED BED OF A CARRIER-SUPPORTED COBALT-MOLYBDATE CATALYST, MAINTAINING CONDITIONS IN SAID REACTION ZONE WHICH CAUSE SAID HYDROGENATED HYDROCARBON FEED STOCK TO BE HYDROGENATED AND SAID DEHYDROGENATABLE HYDROCARBON FEED STOCK TO BE DEHYDROGENATED, CONTINUOUSLY CONTROLLING THE RELATIVE CONCENTRATIONS OF HYDROGEN, HYDROGENATABLE HYDROCARBON FEED STOCK AND DEHYDROGENATABLE HYDROCARBON FEED STOCK IN SAID REACTION ZONE BY INJECTING AT LEAST PART OF AT LEAST ONE OF SAID REACTANTS AT A PLURALITY OF POINTS ALONG SAID REACTION ZONE, SO AS TO DECREASE TEMPERATURE CHANGES THROUGH THE REACTION ZONE AND WITHDRAWING PRODUCTS FROM SAID REACTION ZONE. 